Study predicts more hot spells in Southern California

UCLA researchers say the number of days topping 95 degrees each year will jump by as much as five times. The study could help local governments prepare for extreme temperatures and reduce risk to residents, L.A. Mayor Antonio Villaraigosa says.

By the middle of the century, the number of days with temperatures above 95 degrees each year will triple in downtown Los Angeles, quadruple in portions of the San Fernando Valley and even jump five-fold in a portion of the High Desert in L.A. County, according to a new UCLA climate change study.

The study, released Thursday, is the first to model the Southland's complex geography of meandering coastlines, mountain ranges and dense urban centers in high enough resolution to predict temperatures down to the level of micro climate zones, each measuring 2 1/4 square miles. The projections are for 2041 to 2060.

Not only will the number of hot days increase, but the study found that the hottest of those days will break records, said Alex Hall, lead researcher on the study by UCLA's Institute of the Environment and Sustainability. The record for downtown Los Angeles is 113 degrees, set Sept. 27, 2010, when the Department of Water and Power electricity demand reached a historic peak of 6,177 megawatts.

Mayor Antonio Villaraigosa said the forecasts provide the groundwork for local governments, utilities, hospitals and other institutions to prepare for the hot spells to come. Villaraigosa said the region may have to strengthen building codes to reduce risk to residents. "That could mean replacing incentives with building codes requiring 'green' and 'cool' roofs, cool pavements, tree canopies and parks," he said.

The study, aided by a UCLA supercomputer, is 2,500 times more precise than previous climate models for the region, said Paul Bunje, executive director of the UCLA Center for Climate Change Solutions. The computer made roughly 1 quintillion calculations — the equivalent of eight times all the grains of sand on the beaches of the western United States — over a period of six months to assess every aspect of 25 global warming models that might be applicable to Southern California.

To read the full article in the Los Angeles Times by Louis Sahagun click here.